Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, Washington 98195, USA.
Pacific Northwest National Laboratory, Richland, Washington 99354, USA.
Phys Rev Lett. 2018 May 25;120(21):211804. doi: 10.1103/PhysRevLett.120.211804.
The Majorana Demonstrator is an ultralow-background experiment searching for neutrinoless double-beta decay in ^{76}Ge. The heavily shielded array of germanium detectors, placed nearly a mile underground at the Sanford Underground Research Facility in Lead, South Dakota, also allows searches for new exotic physics. Free, relativistic, lightly ionizing particles with an electrical charge less than e are forbidden by the standard model but predicted by some of its extensions. If such particles exist, they might be detected in the Majorana Demonstrator by searching for multiple-detector events with individual-detector energy depositions down to 1 keV. This search is background-free, and no candidate events have been found in 285 days of data taking. New direct-detection limits are set for the flux of lightly ionizing particles for charges as low as e/1000.
马约拉纳中微子探测器是一个超低本底实验，旨在寻找锗-76 的中微子双β衰变。该实验的锗探测器被放置在南达科他州利德市桑福德地下研究设施的地下近一英里处，探测器被厚重的屏蔽层所包围，该实验也可以用来寻找新的奇异物理现象。在标准模型中，带电量小于 e 的自由、相对论性、弱电离粒子是被禁止的，但在一些标准模型的扩展理论中，这些粒子是被预测存在的。如果这些粒子存在，它们可能会在马约拉纳中微子探测器中被探测到，因为探测器可以通过寻找单个探测器能量沉积低于 1keV 的多探测器事件来探测到它们。该搜索是无背景的，在 285 天的数据采集过程中，没有发现候选事件。对于电荷量低至 e/1000 的弱电离粒子通量，新的直接探测极限已经被设定。
